And I fell at his feet to worship him.
Clearly John is very human and totally out of place during the vision of the MARRIAGE SUPPER. He did what many who have had this kind of brush with purity and righteousness (see Matthew 17:1-6-8 for example) have done. Except here, Jesus was involved in the SUPPER, so John falls down at the angel's feet and that is not good. First, we must WORSHIP GOD and not angels. The worship of angels defrauds the worshipper of their desired goal (Colossians 2:16-18-19).
And he said to me,"Do not do that; I am a FELLOW-SERVANT of yours and your brethren who hold the TESTIMONY of JESUS;
The rebuke is firmly given with sweet humility. The angel is a created being with the purpose to serve God and by extension the redeemed (people who hold the TESTIMONY of JESUS). These who hold the TESTIMONY of JESUS are the same ones with whom the dragon (devil) is making war (Revelation 12:17).
Angels are very aware of their position in heaven. Apparently, they, too, at one time were given a choice: Serve GOD or join the devil (dragon -- Revelation 12:7-9). This angel chose to serve God and, in turn, the redeemed.
Interestingly, John doesn't fully understand what he has done wrong because he will do it again (Revelation 22:8,9).
WORSHIP GOD. For the TESTIMONY of JESUS is the SPIRIT OF PROPHESY."
It is clear where our worship is to be directed: GOD. Anything else is idolatry and violates God's forever commandment (Exodus 20:4-6). The angel here acknowledges that the God he knew from his creation was also sent to earth to assume a human form (denoted by the use of the name JESUS -- Luke 1:26-31-38 and Matthew 1:18-25). The angel emphasizes God as the triune God. WORSHIP GOD (the Father). For the TESTIMONY of JESUS (the Son) is the SPIRIT (Holy Spirit) of PROPHESY. Soon this Holy Trinity will be doing away with the Unholy Trinity (devil himself, Revelation 20:10; beast, verse 20; and false prophet, verse 20).
In a sense, angels, too, do a form of prophesy (Revelation 14:6-12).